Telephone-exchange system



l'l etented l2, ieees ele ALBIEN n. LUNDELL AND Janene creme,

wnsi nnn ELECTR C COMPANY, mconzonncrnn PORATION OI NEW YORK.

'IELEPHONE-EXCEANGE SYSTEIVI Application filed September To all who121x52,- muf cone-em.

Be it known that We. ALnnN E. LUNDELL and lino-x1: H. CLARK, citizens ofthe United States, i siding at lie York, in the county of Bronx, Stateof New York, and at New York, in the county oi New York and State oi'?hie York reepoctirely, have invented certain new and nsel iilImprovements in Teleplione lfixcheiige Systems, of Which the t'ollowinggis :1 full, clean concise, and exact description.

This; invention relates to telephone ex change systems and moreparticularly to improvements in systems employing; nnchine :-s'\vit'-hin;g i I [in object of this invention to provide improved andsimplified means for contro1- ling: con tinnons trunk hunting inautomatic H.\'lt(7ll(-3S. l

.Another object is to provide simple means for varying the fine of:group of trunks over which continuous hunting is to take place.

ficcorrlinn to one feature oil the invention, at pair of relays areorieniyeiil jointly to control the action of third relay and to controlthe COllilIlHOHH Hunting movement of the switch over groups oi variablesize. The third relay is also responei e to the electrical condition ofthe ti minzile over which hunting occurs and an. vitch when a desiredset ie reached.

lreretjot'oi'c, in switches which provided "for continuous trunkhunting", it ha been the practice to design the stri'ictnre to pern'iithnntinej over oronps -(ich containing a fixed lli'lililiii' otteroiinzile. Win-2n trntlic increziseil .--'o that the mimher oi'ei'i'i' imils in'zt group was not siiliicitnij to hand e the mills, andit '25 oesircil to lil'ltflf-{Q the nim'iher in each group. kllill'lfi'eb were neccrsszinv in the striiciiii'e of the switch. Ac coriii'igx to the prceent intention, no strut tn z l change is 119(OHSH1'Xto vary the the gri'oiipe, but only :i slight circuit 15 i he (ha-urineii; n dineraninxzitic repreientzition of on en' li odiinent oi the'inven' tion applied to a telephone exchange systern employing switchesof the panel type. but it is to he understood that the invention is notlimited in its-scope to such systo stop the i'oi-o an operator.

6,1919. Serial No. 322,039.

terns but might readily be applied to systems employing any form ofmachine switching.

Attheleft of the dotted line in the drawing, is shown in abbreviatedform, appeetns'et av substation a central office ones etors cord circuitand a; district selector switch S for connecting the substation to theincoming selector S. "These selector 'itches may he of the panel typefully die closed in the patent to Craft and Reynolds No. 1,123,696 ofJanuary 5,1915.

iVithin the dotted rectangle; 2L sender is shown. Onlyon upper erocounting relay 1, i stepping relay 2 and a sequence switch contact 3' ofthe sender are shown herein. The Contact?) is controlled by it sequenceswitch (not shown) associated With the sender, WhlCll lS in turncontrolled through the front contact end armature of relay 1. The othergequence eiritch contacts indicated to the left oi the dotted line arecontrolled hy the district selector sequence switch (not shown). Thesequence switch cont-net indicated to the right of the dotted line arecontrolled by sequence sirit 1h NM). 'The' sequence switches referredto. may he .ot the typedisclosed in the patent to Reynolds and BaldwinNo. .5121808 of l elzi'nziry 1), 1915. The circuits emplo edinoperating' the sender and district se tor :iice fully disclosed in the{BREE/Ill to Lint-dell lio. l ltifdfilof January i8, lfi'i it isbelieved that the invention will. he readily understood. from thetollowing description of the operation of the Sj/SlQl'IL A subscriberatstation A desiring a conneetioin removes his receiver from thesiritchhook and completes 2t circuit "for the line relay 5 which lightsthe onlllamp 6 be- The operator noticing the lit-n p 6, inserts her plug9 in the answer mg; jack 9" and inquires the desired nnmhei: :l 'heinsertion ofplng 8 into jack 9 completes. a circuit for relays 7 and 10.."Beley 7 cuts oil": the line relay and extinguishes the cell lamp. Therelay 105mm the district selector sequenceswitch, the contacts of whichare indicated at the left-hand side of the dotted line. Under thecontrol of this sequence switch, the sender is associated withthejdistrict selector and'the operator new sets the sender in accordancewith the number of the called line. The brushes 13,-

14 and 15 of the district selector are then set in the well-known manneron the terminals 16, 17 and 18 of an idle trunk leading to the incomingselector S, in the banks of which are terminals oftrunks leading toswitches through which a connection with the desired line may becompleted. 3 i

After the setting of the selector S,'its sequence switch-will be inposition 7, A circuit is thereupon completed from grounded battery,through the winding of relay 4, sequence switch contacts 19 and 20,conductor 21, sequence switch contact 3, winding of stepping relay 2,back contact and armature of relay 1 to ground Relay 4 is energized andlocks up over a circuit through its right-hand front contact andarmature, sequence switch contact 22, and; the circuit just traced.Relay 4 in energizing, moves the district selector'sequence switch, outof position 7 into position 8'; i" A circuit is thereupon completed fromground, left-hand armature and front contact 01 relay 4, contact 23,brush 13, terminal 16,,conductor 56, contact 24, conductor 25, contact26, through the righthand winding of line relay 27 to grounded battery.Line relay 27 vis energized in vthis circuit and lockedup through itsright-hand armature, conductor 28, contact 29, contact 30, conductor 25,through the circuit just traced to ground, at the left-hand armature Inenergizing, relay 27 compower magnet of sequence switch 100, contact 31,front contact and inner left-hand armature of relay 27 to ground, todrive the sequence switch 100 out of position 1, into position, 2 underthe control of its master contact 32. In position 2 of sequence switch;

100, a circuit is completed for the up-drive magnet 33 of the incomingselector switch which may be traced from grounded battery, magnet,- 33,back contact and outer right-hand armature of relay 34, contact 36,front contact and inner left-hand armature of relay 27 to ground. Magnet33, in operating, presses driving ribbon 37 against a roller, 33 whichisconstantly rotating in the direction indicated by the arrow,-to elevatebrush rod v39, with its associated sets of brushes. Each time that thebrush 47 passes. a conducting segment of commutator- 50, ground isconnected over the following path: brush'47, commutator 50, contact 54,conductmh-fifi, terminal 17, brush 14, contact 58.x. This ground. holdsup relay 4, but shunts stepping relay 2'to operate. the count ingr.relays" in. the well-known manner. \Vhen the last counting relay 1 isenergized,

the fundamental circuit is-broken at the armature and back contact ofrelay 1 and relay 4deenergizes to move the district selector sequenceswitch into position 9. At

its, iei't-hand armature, relay 4 opens the circuit of relay 27 whichdeenergizes, opennet of sequence switch 100, contact 59, baclc contactand outer left-hand armature of relay 27, conductor 6O, contact 61toground. The desired set of brushes, of which only one set 40, 41 and42 is shown, is now in position to be tripped, and the trip rod magnet62 is energized over a path from grounded battery, winding ofmagnet 62,contact 63 to ground, so that the brushes will be tripped upon the nextupward movement of the brush rod 39.

lVith the district'sequence. switch in position 9, a circuit is againcompleted for relay 4 which energizes and locks up over the pathpreviously traced. In energizing relay 4 moves the" district sequenceswitch into position 10. A circuit is then completed from groundedbattery, through the righthand winding of relay 27, contact 26, and thecircuit previously traced to ground, at

the letthand front contact and armature of rela 4. Relav 27 ener izesand locks u in y a P the manner previously described. A circuit is nowcompleted from grounded battery, winding of sequence switch 100,concircuit previously traced to" shunt stepping relay 2, until relay 1again operates to break the fundamental circuit and to deenergize relay4. As before, relay 27 deenergizes to more sequence switch into position5, and to open the circuit of magnet 33. The test brush '42 is now inengagement with an intermediate terminal46, just below the terminalsoiithe group ottrunlrs leadingto the desired final selector switches.

lVith the sequence switch 100 in position 5. a circuit is completed toenergize relay 27 from grounded battery, lefthand wind-- ing of relay 27contact 64, back contact and outer righthand armature of relay 3:), backcontact and inner right-hand armature of relay 34 to ground. Relay 27 inenergizing. completes a circuit previously traced to move sequenceswitch 100 out of position 5 into position 6. In position 6, the circuitof Lip-drive magnetz33 is again completedto drive the brushes ()"11 theterminals in the Selected group, to seek an idle trunk, which will bedistinguished by absence of potential, the busy trunks beingdistinguished by ground potential. Line relay. 27 looks up over acircuit from grounded battery, through its righthand winding, frontcontact and armature, conductor 28, contact 29, contact 65, testconductor 66, brush 42 and test terminals 45 of busy trunks. As soon asthe brushes startupward, brush 48 leaves the insulating segment ofcommutator 51, upon which it was resting, and a circuit is completedfrom ground, brush +i8, conducting segment of commutator-51,.conductor67, contact 68, conductor 69, lefthand armature and back contact ofrelay 34, winding of relay 35, through the righthand winding of relay togrounded battery. Relay 35 is energized in this circuit, but relay 34 isnot, since its right-hand winding is marginal, and will not pull up therelay but serves only as a holding wind ing. Relay 35, in energizing,breaks the circuit over which the left-hand winding of relay 27 wasenergized and leaves the line relay 27 under the control oi the testcircuit.

It now there is an idle trunk in the group being hunted over, thecircuit through the right-hand winding of relay 27 will be broken whenits terminals are reached. Belay 27' is held up for a moment longer,however, over a circuit from grounded battery, left-hand winding ofrelay 27, contact 70, conductor 71, conducting segment or" commutator 52and brush {L9 to ground. VVheu brush 4%) leaves the conducting segmentoil commutator 52, this circuit is broken and relay 27 deenergizes,breaking at its inner lct't-hand armature and front contact the circuitof the updrive magnet 33, and stopping the switch with its brushes inengagement with the terminals of an idle trunk. The insulating segmentsof the commutator 52 are so positioned, that the brush 49 will only reston one, when brushes 4:0. 4:1. and 4L2 are accurately centered on a setof terminals 4:3, 414 and 45. Relay 27 in deenergizing completes acircuit from ground, inner right-hand armature and back contact of relay34, outer right-hand armature and front contact of relay conductor 72,conductor 60, contact 83. contact Set. back contact and right-handarmature of relay 27, conductor 28. contact 29. Contact 65, test brush4:2 and test terminal 45 ot the selected trunk. This application 01grouiul to the test conductor of the seized trunk, renders this trunkbusy immediately upon its seizure. It will be remembered that relay 35was energized during the upward travel of the brushes, so that upondeenergization ot relay 27, a circuit is completed from groundedbattery, magnet of: sequence switch 100. contact 59, back contactandouter left-hand armature of relay 27, .con-

ductor 72, front contact and outer righthand armature of relay 35, backcontact and inner right-hand armature of relay 3a to ground, to movesequence switch 100 out of position 6, into position 7 In position 7,the circuit of relay 35 is broken at contact 68 and it deenergizes tocomplete a circuit from grounded battery, left-hand winding of relay 27,contact 6st,.back contact and outer right-hand armature of relay 35,back contact and inner right-hand armature of relay 3% to ground. Relay27 is energized and locked up over a circuit from grounded battery,right-hand winding, front contact and armature of relay 27, conductor28, contact 29, contact 73, over the test conductor 57, terminal 18, andbrush 15 to the ground which was connected to this brush, when thedistrict selector switch S was set. In energizing, relay 27 completes acircuit from grounded battery, power magnet of sequence switch 100,contact 31, front contact and inner left-hand armature of relay 27 toground, to move sequence switch 100 into position 8. In position 8, thesender is again operated in the wellknown manner to set the finalselector switch on the terminals of the desired line. Conversation maynow take place. At the close of the conversation, the operator isnotified in the well-known manner through the operation'ot supervisoryrelays l1 and 12, and removes plug 8, from jack 9. Inso doing, sherestores the district selector switch ti. thus removing the holdingground from the brush l5 and line relay 27, which deenergizes. Indeenergizing, relay 27 completes a circuit from grounded battery powermagnet of sequence switch 100, contact 59, back contact and outerleft-hand armature of relay 27, conductor (SQ contact 61 to ground, tomove sequence switch 'lOOinto position 18. In position 18, a circuit forthe down-drive magnet 7a; is completed from grounded battery, winding ofmagnet 74, contact 75, to. ground. The magnet 74: is energized andpresses the driving ribbon 37 against the constantlyrotating roller 76to restore the brushrod and brushes to normal position. When thisposition is reached, a circuit is closed "from grounded battery, magnetof sequence switch 100. conductor 77, contact 78, cont inutator 79,brush. 417 to ground, to move sequence switch 100 out of position 18,back to normal, at which time the system is ready for the next call.

It will be remembered that huntingfor an idle trunk began, with sequenceswitch 100 in position 6, with relay 27 locked up through its right-handwinding to test brush l2 and the test terminals of busy lines and withrelay energized over a circuit extending from a conducting segment ofcommutator 51 and conductor '67,

travel of the bushes, however, since this circuit is shunted. by aground appliedthrough the left-hand armature and back contact of relay34:.

If no idle trunk is found, brush set 40, 4:1

and 12 will continue its travel until an intermediate terminal such as46, at the end of the group, is reached. In passing from the last busytest terminal a5 of the group tested, to the intermediate terminal. d6which is distinguished by absence of po tential, brush 42 breaks theholdingcircuit through the right-hand winding of relay v 27. This relaydeenergizes, opening at its I inner left-hand armature the circuit forup drive magnet 83' and stopping the switch.

Brush 48' comes to rest on an insulating segment of commutator 51, thusremoving the shunt from the left-hand winding of relay 34E, whereuponthis relay isenergized in series with relay 35 over the circuit preparedwhen relay 35 was energized. Belay 34 energizes so soon after thedeenergization of relay 27 that the circuit whichwas I110- mentarilyclosed for the power magnet of sequence switch 100 over the back contactand outer leftshand armature of relay 27 is ineffective. from groundedbattery, left-hand winding ofrelay 27, contact 64, front contacts andinner righthand armatures of relay and relay 34: to ground, to energizerelay 27. Thisrelay completes the circuit of downdrive magnet 74 fromgrounded battery, winding of magnet'7, front contact and outerright-hand armature of relay 34, contact 36, front contact andinner'left-hand armature of relay 27 to ground. Magnet74 is energizedand carries the brushes downward over the group of trunk terminals. Assoon as brush 48 leaves the insulating segment of commutator 51, uponwhich it was resting. a circuit completed from ground. brush 48,commutator fifh'conductor 67, con tact 6'8, left-hand armature and frontcon tact of relay 34, right-hand. winding of relay 34, to groundedbattery, thus shunting the left-hand winding of relay 34 and winding ofrelay Relay 35 deenergizes, but the right-hand winding of relay 34 issuflicient to hold up this relay. In deenergizing, relay 35 opened thecircuit through the left hand winding of relay 27 and transferred thecontrol of thisrelay to its right-hand winding, which is locked up toground on A circuit is now completed busy terminals. If an idle terminalis now found, the circuit through the right-hand winding of relay 27 isbroken, due to ab- 8611 66 of potential on test contacts of idle lines.Relay 27 is held up momentarily over a circuit from grounded battery,left-hand winding of relay 27 contact 70, conductor 71, conductingsegment of commutator 52, brush 49 to ground, until the brushes 40, lland 42' are accuratelycentered on the idle set of terminals, atWhichtime brush 49 reaches an insulating segment of commutator52,0pening the circuit of relay 27. Relay 27 thereupon deenergizesbreaking at its left-hand armature and front contact, the circuit ofdown-drive magnet 74 and stopping the brushes on an idle trunk terminal.Relay 27 in deenergizing, applies ground to the test conductor of theseized trunk to hold said trunk busy, over the following circuit: groundinner right-hand armature; and front contact of relay 34-,

inner right-hand armature and back contact of relay35, conductor72,conductor 60, contact 83, contact 84, back contact and right-handarmature relay 27, conductor 28, contact 29, contact 65, conductor 66,brush 41-2 and 'test terminal 45. -From this point, the operation is thesame as in the case previously described, when an idle terminal wasfound in the. upward hunting movement. I 1

Ifno idle terminal is found in the downward hunting movement, thebrushes travel until they reach the intermediate terminal 46 the endofthe group, atwhiclrtime the holding circuit of relay 27 is broken aspreviously described. As thebrush 48 comes to rest on'an insulatingsegment of commutater 51 immediately after the deeneigization of relay27, the holding circuit through the right-hand winding of relay 34, itsfrontcontact and left-hand armature and conductor 67 is broken at saidinsulating segment and relay 34E deenergizes. vRelays 34 and 35 are nowboth in deenergized condition, the brushes are resting on theintermediate terminal at the bottom of the group of terminals which areto be huntedover, and the condition of the system is exactly the same asdescribed when sequence switch 100 first reached position 6. Relay 27 isagain energized through its left hand winding and theback contacts and.right-hand armatures of relays 35, and 34k, and hunting is continueduntil an idle trunk is found, on either the up or down movement of thebrush shaft.

We have so far assiuned that only one group of terminals-is to be huntedov- 1' con tinuously, regardless of Whether any idle terminals are foundor not. When trafiic conditions become so heavy that it. he quentlyoccurs that no idle trunk will be found in a group of terminals of thesize originally designed to be hunted over, the

group of tern'iinals to be hunted over may be enlarged to twice itsoriginal size, or as many times more as is desirable, by simplyconnecting ground to intermediate test terminals 426 between the groupsof terminals which are to be consolidated into a single group, noground, however, will appear on the terminals .1-6 which are to definethe limits of the new group.

The operation up to the time when sequence switch 100 moves intoposition 6 is the same as described for the smaller group of terminals.When sequence switch 100 is in position 6, the circuit completed fromgrounded battery, left-hand winding ofrerelay 2?, contact Get, backcontact and outer right-hand armature or relay 35, back contact, innerright hand armature of relay 34C to ground to energize relay 27. Belay27, in coming up, completes the circuit for updrive magnet 83 and locksup through its right-hand winding, front contact and armature to groundat busy test terminals .51 5, as before. Ground is applied through thebrush 48, conducting segmentof commutator 51, to the left-hand armatureand back contact of relay 84-, as before, and relay v35 is energized. If.an idle trunk is found .in the first subgroup hunted over, relay 27deenergizes as before,-to stop the. switch. If no idle trunk isfound,,the intermediateterminal efibeing now groundechholds up re:

lay 27 to continue the travel of the brushes into the next sub-group.Brush 48 encounters an insulating segment of commutator .51 as beforebut removal of the ground connected from brush {l8 and the conductingsegment of commutator 51ito the letthand armature v and back contact 1of relay 34; does not, however, ,remove the shunt frpm the leftwindingofthis relay, as in the case previously described, since a substituteshunt circuit is provided traceable from grpund, inner right-handarmature and back contact of relay 34;,puter right hand,armatureandfront contact oi? relay 35, ,cond'uctor 72, enter left-hand armatureand. trout contact of relay 27, contact 82, contact fis, conductor69,;back contact andileft-hand armature of relay S L. Thus relay -35 isheld energized throughout the, upward traveler the brushes and relay 34;has anenergizing circu t prepared to operate at the; removal ,of ,theground through commutator 5l whenan 1nsulating segment of saidcommutator s reached by, brush 4L8, v at ,altime. when relay Ellisdeenergized. If no idle terminal found throughout the entire enlargedgroup, the. brushes travel upward, unt l the intermediate terminal, l6,,at the end ,of the group, is reached, at which time no potential beingfound at terminal to, the holding cir cult for relay 27 is broken todeenergizethis i'e ay. Relay 27, in leenergizing, breaks at w asel haudwinding, this relay comes up in series with relay :55 over the circuitfrom grounded, battery, right-hand winding of relay 3-}, winding ofrelay' left-hand winding of relay 34:, left-hand armatureand contact ofrelay 35, contact to ground. The lefthand winding of relay 27 is nowenergized over the circuit extending through the front contacts andright-hand armatures of relays 35 and 34;, as previously described, andthe circuit of down-drive magnet 74- is also completed over thepreviously traced circuit. As soon as brush {l8 leaves the insulatingsegment of commutator 51, ground is applied oyer the circuit previouslytraced through the left-hand armature and front contact of relay 34, tohold up this relay and to shuntrelay .35 which deenergizes. Whensubsequent insulating segments of commutator 51 are traversed, asubstitute circuit to hold up relay may be traced from grounded battery,right-hand winding of relay 3%, front contact and left-hand armature ofrelaytg conductor 69, contact 68, cont-act 82, outer left-hand armatureand front contact of relay 27, conductor 72, back contact and vinnerright hand armature of a relay 35, front contact, andinner right-handarmature of relay T 84 to ground. Thus, re-

34 is held up until this holdingfcircuit is broke'n' by thedeenergizjation of relay 27, caused by thefinding of,'anidleset of trunkterminals or of an intermediate test contact 46 at the enclottheenlargedgroup which ,is distinguishedby absence ofpotentiall It will thus,beseenthat the number of tern inals, in a group which is, to be, huntedover continuously, may be changed without chan '1 the structure of theswitch, by the simple applicationlot ground potential "to saidintermediate contacts for determining whether the back and itorthmoueinentiis to extend over one or a plurality of said groups.

29111 a telephone system, an automatic switch, a plurality of telephoneslines (lb rided into groups terminating in fixed contacts in saidswitch, contacts lntermediate telephone lines,

said groups, means for moving said. switch ina continuous reciprocatingmovement over, said contacts to hunt an idle line, andineans operatingin response to the electrical condition of said intermediate contactstor limiting the movement ofsaid switch in one direction.

' 3. In atelephone system, a selector switch having a directive and anautomatic movement, a plurality of trunk lines accessible to saidswitch, means for directly setting, said switch, means for automaticallym ring said switch back and forth in a continuous reciprocating movementto hunt an idle trunk, and electrical means for varying the number oflines passed over by said switch in its hunting movement.

l. In a telephonesysteimtclephone lines, an auton'iatic switch in whichsaid lines terminate in contacts, brushes arranged to travel over andmake contact therewith, a source of power, a relay, a'circuitforvopcrating said relay to associate said source of power with saidbrushes to move them in one direction, a circuit for holding said relayto move "them in the opposite direction.

5. lnfa telephone system, telephone lines,

an automatic switch in which saidlines terminate in contacts, brushescooperating with said contacts,a power circuit, a relay to coin trolsaidxpower circuit, a pair of relays and a circuit arrangement thereforincluding a break point whereby two successive closures and openings ofsaid break point will cause "said relaysto be successively actuated inall possible combinations, a circuit for said power controlling relayalternately closed I and opened in successive combinations of actuationof said pair of relays, means for initlally closing said circuit, 'asecond C11! cuit for said power controlling relay responsive to theelectrical condition of saidcontacts, a source of power for moving saidbrushesin one direction, a source of power for movingsaid brushes in theopposite d' iGCiZlOIl, means responsive to the condition of one of saidpair of relays for including alternately said first source of power orsaid second source of power in said power circuit, and means positionedin, accordance with the position of said brushes for successively closing and opening said break'point.

6. In a telephone system, telephone lines,

reversing its movement.

an automatic switch in' which said lines terminate in contacts, brushesarranged to travel over and make contact therewith, a source of power, arelay, means for operating said relay to associate said source of powerwith said brushes to move them in one'direction, means actuated when apredetermined number of said contacts have been passed tooperate saidrelay as a result of the engagement of said brushes with a particularcontact set to dissociate said source of power from, said brushes, andmeans thereupon" actuated for operating said relay to associate saidsource of power with said brushes to move them in the oppositedirection. I I

7. In a telephone system, telephone lines, an automatic switch in whichsaid lines terminate in groups of fixed contacts, contacts intermediatesaid groups of contacts, means for moving said switch over a group ofcontacts, and means controlled by the electrical'condition of saidintermediate contacts for continuing-the travel of the switch or forreversing its movement; I

8, In a telephonesystem, telephone lines, an automati'c switch in whichsaid lines terminate in contacts, means for moving said switch over apredetermined number of-said contacts in a continuous reciprocatingmotion, and means responsive to the electrical condition of certain ofsaid contacts for continuing the movement of said switch or for 9. Inatele'phone system, groups of trunk lines, an automatic switch in whichsaid lines terminate in contacts, a contact intermediate -adjacentgroups of trunk contacts,

means for moving said switch in a continuous reciprocat ng motion over asingle group of trunk contacts, and means controlled by the electricalcondition of'said intermediate contact for extending said movement overan adjacent group of contacts.

10. In a telephone system, equivalent and norrequivalent groups oftrunks, an auto- I'hatlOSWitCh in which said trunks terminate with theterminals of equivalent groups adjacent, a contact intermediate saidgroups,

means for moving said switch over each non equivalent group of terminalsin a continuous reciprocating motion and means controlled by theelectrical condition of said intermediate contact 7 for continuing thetravel of saidswitch over and adjacent group of equivalent trunkterminals.

11. In a telephone system, a switchhaving a non-numerical movement, aplurality of telephone lines terminating in said switch, a

set of wipers arranged in operative relation to said lines, a source ofpower for moving said wipers, means for applyingsaid source ofpower tomove said wipers in one direction, means for disconnecting said sourceof power from'said wipers, means for there upon applying said source ofpower to move said wipers in an opposite direction, means for causingsaid wipers to seize an electrically distinguished one of said telephonelines while moving in either direction, and electrical means for varyingthe number of said lines Over which said. wipers may move in eitherdirection before initiation of movement in the opposite direction.

12. In a telephone system, equivalent and non-equivalent groups oftrunks, an automatic switch in which said equivalent and non-equivalenttrunks terminate with the terminals of equivalent groups adjacent, contacts intermediate each group of trunks, brushes for said switch forcontacting with said terminals, a source 01. power, a relay, a circuitfor operating said relay to apply power to drive the switch, a circuitincluding a contact between equivalent groups and said relay closed tomaintain said source of power applied to continue the movement of theswitch, and means for opening said circuit to render said relay inert tostop the matic switch in which said trunks terminate with the terminalsof equivalent groups ad jacent, means including control relays formoving said switch, acircuit for maintaining the control relays in acertain condition during the movement of the switch, means for openingthe circuit when the end of a group is reached to change the conditionof said control relays to reverse the direction of movement, and meansfor closing a substitute circuit to maintain the control relays incondition to keep the switch moving in the same direction to test theequivalent group when the switch reaches the end of a group preceding anequivalent group.

In witness whereof, we hereunto subscribe our names this 4th day ofSeptember A. D,

ALBEN E. LUNDELL. EDGAR H. CLARK.

